There's a bit of a story going on between Google, Acer, and Alibaba, a Chinese mobile operating system vendor. Acer wanted to ship a device with Alibaba's operating system, but Google asked them not to, and Acer complied. The reason is that Acer is a member of the Open Handset Alliance, which prohibits the promotion of non-standard Android implementations - exactly what Alibaba is shipping. On top of that, Alibaba's application store hosts pirated Android applications, including ones from Google.

Yet the company says: “Aliyun OS incorporates its own virtual machine, which is different from Android’s Dalvik virtual machine. Aliyun OS’s runtime environment, which is the core of the OS, consists of both its own Java virtual machine, which is different from Android’s Dalvik virtual machine, and its own cloud app engine, which supports HTML5 web applications. Aliyun OS uses some of the Android application framework and tools (open source) merely as a patch to allow Aliyun OS users to enjoy third-party apps in addition to the cloud-based Aliyun apps in our ecosystem.”

So that would then not make it a fork.

Yes, it is to be expected that the statements by Google would be denied by Aliyun's maker (which is why I said "apparently they didn't re-implement a new VM"). A first-order determination of whether a given code-base is derived and altered can be made pretty quickly (a simple "strings" dump will do it), but since we lack the binaries in question to do an actual confirmation, all we have are statements against statements.

Nevertheless, even without a VM, they admitted openly to incorporating (at least some of) Android's frameworks and tooling as a drop-in, so Google clearly has a case here. Let's keep in mind, that these aren't just a few lines of code, it's a substantial and non-trivial codebase.

Therefore, the case is quite dissimilar to Oracle v. Google. There, Google didn't copy anything from Oracle's implementation (save for a few lines of a range-check macro), and Oracle has a patent grant on Java predicated on adherence to an interoperability specification.

The Aliyun OS lifted wholesale substantial portions of the Android codebase and Google has no such patent grant for Android (i.e. one based on compatibility testing), so there is no legal leverage that can be used against downstream forks. The only leverage they have is revocation of membership in the OHA, which is not something anybody can sue over.